Ref: https://learn.cantrill.io/courses/1820301/lectures/41301501

• Summary:
• Contents:

TGW - Key Concepts

• 🔧 NW Transit Hub to connect VPCs with each other and to on-premises NWs
  • Connection to on-prem NWs via S2S VPNs and DX
  • 👍 Important benefit: Significantly reduces NW complexity
• Single NW object (like IGW)
  • HA in region, resilient, and scalable
• Connects to other NW objects via Attachments
  • VPC attachments, S2S VPN attachments & DX GW attachments
• Features
  • Come with default Route Table → how traffic is routed between attachments
    • Can use multiple RTs to create complex routing topology
  • ‼️ Supports transitive routing!! Throughout VPCs and on-prem NWs!
    • No need to create complex NW mesh topologies
  • Integration with DX GWs (uses transit VIF)
  • Can be used to create global NWs → TGW peering
    • Cross-region & cross-account support!
    • Cross-region data uses AWS global NW → higher performance than internet
  • Share TGWs between accounts using AWS Resource Access Manager (RAM)
    • 💡 AWS RAM = service which allows cross-account sharing of products & services

TGW Network Complexity Example

Network Topology without TGW

• VPC peering NOT transitive → every VPC must peer with all others → scales poorly
• Many VPN tunnels
  • S2S VPNs also NOT transitive → must also connect to every VPC
  • Two CGWs required for HA
• 💡 Full mesh network is complex → lots of admin overhead
  • Scales very badly the more VPCs and on-prem NWs you add

Network Topology with TGW

• ❗ ONE single TGW
• S2S VPN attachment → TGW is the AWS-side termination point for VPN (no longer VGWs!)
  • Much fewer VPN tunnels… while still being HA!